Crushed concrete is a very good substrate for a slab. The key is to not have chunks so large that air pockets are created. Maybe bring in a layer of sand to fill the voids and level things a bit. A water rinse will help bring air out and compact the material.
Can you use broken concrete as sub base?
It will be fine.
Can you connect old concrete to new concrete?
You can join the new concrete right to the old concrete, this is called a concrete construction joint. The edge of the existing concrete that was sawed should be drilled and doweled so the new concrete won’t separate, lift, or settle from the old concrete.
How do you use old broken concrete?
Making Walkways or Patios
Large chunks of old concrete work as a substitute for pavers or stones in a patio or walkway. Broken concrete is typically irregularly shaped, so it looks a little like flagstone. Use the concrete pieces as you would use pavers.
Can you use gravel as a sub base?
If your builder uses the gravel he may find it will dissipate too easily into the ground and will spend more time and money to get the levels needed. I would not advise using the gravel. A well constructed base means your drive will never get sink holes.
Can you put a thin layer of concrete over existing concrete?
Yes, you can put new concrete over old concrete providing there are no issues such as significant cracks of frost heaves with your existing concrete. A new layer of concrete should be about two inches to ensure an even, strong coverage.
Can you pour concrete over broken concrete?
You can put new concrete over old concrete. However, unresolved issues with your old concrete, such as cracks or frost heaves, will carry over to your new concrete if not taken care of. In addition, you must pour it at least 2 inches thick.
Can I use 20mm gravel as a sub-base?
0-20mm ballast is perfect for sub-base and concrete foundations. 20mm screened ballast is versatile and can be used on driveways, footpaths, oversite fill as well as sub-bases.
What can be used for sub-base?
Unbound granular materials are usually crushed stone, crushed slag or concrete, or slate. Cement-bound materials come in multiple types. Mass concrete is used where exceptional loads are expected, with thickness usually 100 to 150 millimetres (4 to 6 in), and optional reinforcement with steel mesh or polymer fibers.
How deep should a sub-base be for a concrete slab?
100mm
Preparing the concrete base
As a rule; your base must be 75mm larger that the finished slab to allow for formwork. Clear the area of stones and plants and excavate to a minimum depth of 100mm (deeper for soft ground).
Is sand a good base for concrete slab?
As a general rule, stay away from using sand as a subbase. You’re better off using gravel; your concrete will last longer and have less of a chance of cracking over time.
How do you compact crushed concrete?
Compact and rake.
The simplest way to do this is by driving over your driveway a few times. You could also use a roller for this process. After you’re satisfied with this step, you should rake the crushed concrete to create a slight peak in the center. This will help with drainage when it rains.
Can you pour concrete directly on dirt?
Long story short, yes you can pour concrete over dirt.
What happens to soil under concrete?
As the soil settles or is carried away by other means a gap opens up between the soil and the bottom of the concrete slab resulting in a loss of support. Un-compacted fill dirt, erosion, burrowing rodents, decaying organic material even a loss of moisture in the soil can create voids.
Is gravel required under concrete?
You do need gravel under a concrete slab, footing, or patio. Gravel provides a solid foundation for your concrete as it can be compacted. It also improves drainage, preventing water from pooling beneath the concrete.
Can I lay concrete slabs on soil?
While it is possible to lay paving slabs on soil, it is not generally advised. The durability of any paving with a soil base can depend on many factors, including: Type of soil: Heavy clay soil will be far more durable and less likely to be compromised by British weather conditions.
Can I lay slabs on old concrete?
it will be fine to lay the slabs over the original concrete as long as you have 150mm between the path and the dpc height which is your internal floor height. you are best laying these on a 50mm concrete screed so that it is all keyed together.
Can you lay paving slabs on a dry mix?
I’ve just laid my patio on to a dry mix – works quite well. The ratio can be as low as 1:10 (1 cement, 10 sharp sand), or as high as 1:3, depending on the amount of foot traffic you expect, and what the sub base is like.
